Engineering high-Q surface acoustic wave (SAW) resonators for superconducting circuits, part 2

Mechanical resonators are promising bosonic quantum resources for circuit-QED, featuring small footprints and excellent integration compatibility. However, the state-of-the-art resonators often face a trade-off between large coupling strengths (g) and high mechanical quality factors (Q). In addition, unless carefully engineered, quantum acoustic systems typically exhibit spurious modes which might cause unwanted interactions with superconducting circuits. Following the design and initial measurements of the SAW resonator, in the second part we will focus on the quality factors of these resonators measured with low intracavity phonon number and discuss the features of two-level systems (TLSs) in our resonators. Furthermore, we will introduce single mode SAW resonators with minimal diffraction losses and comparable Qs, which is ideal for strong coupling to superconducting circuit elements.